Florian Thauvin played a part in all four Newcastle goals against Northampton
Florian Thauvin scored on his full debut for Newcastle as the Premier League side beat Northampton to reach the third round of the League Cup.
Thauvin, a £12m signing from Marseille, was involved in all four Newcastle goals, volleying the hosts ahead before crossing for Siem de Jong to head in.
Marc Richards pulled one back from the spot after Cheick Tiote's handball.
But Thauvin set up Daryl Janmaat and Mike Williamson after the break to send the Magpies through with ease.
The France Under-21 winger, who made his debut off the bench in Saturday's 0-0 draw at Manchester United, was a constant menace and scored his first goal in English football just three minutes into his first start.
The 22-year-old, who also provided crosses for each of the other three Newcastle goals, lasted 65 minutes before being withdrawn to a standing ovation at St James' Park.
The League Two Cobblers had looked in contention when Richards's penalty pulled the score back to 2-1 with only 10 minutes gone, but the Premier League side's superiority shone through in the second half.